The present disclosure relates to the field of radiography and, in particular, relates to computer tomography scanners. Even more particularly, the present disclosure relates to an x-ray collimator for use as part of a computer tomography scanner, and a method of manufacturing an x-ray collimator.
In computed tomography, a patient to be examined is positioned in a scan circle of a computer tomography (CT) scanner. A shaped x-ray beam is then projected from an x-ray source through the scan circle and the patient, to an array of radiation detectors. By rotating the x-ray source and the collimator relative to the patient (about a z-axis of the scanner), radiation is projected through an imaged portion of the patient to the detectors from a multiplicity of directions. From data provided by the detectors, an image of the scanned portion of the patient is constructed.
Within the x-ray source, an electron beam strikes a focal spot point or line on an anode, and x-rays are generated at the focal spot and emitted along diverging linear paths in an x-ray beam. A collimator is employed for shaping a cross-section of the x-ray beam, and for directing the shaped beam through the patient and toward the detector array.
Conventional collimators generally comprise a plate of material that attenuates or absorbs x-rays, such as a lead alloy, tungsten or a tungsten carbide. The plate is provided with one or more slits for shaping cross-sections of x-ray beams. Dimensions of the slits must adhere to tight tolerances to produce precise beam cross-sections.
If the collimator is made of a very hard material, such as tungsten or a tungsten carbide, then expensive machining methods such as wire electrical discharge machining must be used to manufacture the collimator.
What is desired, therefore, is a collimator that produces precise beam cross-sections, yet that is less expensive to manufacture.
The present disclosure, accordingly, is directed to a collimator and a method of manufacturing a collimator that address and overcome the limitations of conventional collimators. In particular, the present disclosure provides a collimator for collimating a beam of energy. The collimator includes a plate-like body, a coating of x-ray absorbing material covering a predetermined portion of a surface of the body, and at least one slit for collimating the emitted beam, with the slit extending through the coating and the body.
The present disclosure also provides a method of manufacturing a collimator. The method includes providing a plate-like body, and coating a predetermined portion of a surface of the body with an x-ray absorbing material. The method also includes machining at least one collimating slit through the coating and the plate-like body.
A collimator constructed in accordance with the present disclosure produces precise beam cross-sections, yet is less expensive to manufacture.